'Hourglass' Shaped Craters Filled Traces Of Glacier

A new image, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, shows flow features most likely formed by glaciers or 'block' glaciers.

Share:

Total shares:

FULL STORY

'Hourglass' shaped craters filled with traces of glacier.

Credit: s: ESA/DLR/FU Berlin (G. Neukum)

'Hourglass' shaped craters filled with traces of glacier.

Credit: s: ESA/DLR/FU Berlin (G. Neukum)

A new image, taken by the High Resolution Stereo Camera (HRSC) on board ESA's Mars Express spacecraft, shows flow features most likely formed by glaciers or 'block' glaciers.

This unusual 'hourglass'-shaped structure is located in Promethei Terra at the eastern rim of the Hellas Basin, at about latitude 38º South and longitude 104º East. A so-called 'block' glacier, an ice stream with a large amount of scree (small rocks of assorted sizes), flowed from a flank of the massif into a bowl-shaped impact crater (left), nine kilometres wide, which has been filled nearly to the rim. The block glacier then flowed into a 17 kilometre wide crater, 500 metres below, taking advantage of downward slope.

The Martian surface at mid latitudes and even near the equator was being shaped by glaciers until a few million years ago. Today, water ice could still exist at shallow depths as 'fossil' remnants of these glaciers.

Numerous concentric ridges are visible and appear similar to 'end moraines' (hills of scree that form as an extending glacier pushes material ahead and remain after its retreat). Furthermore, there are parallel stripe-like structures that are interpreted as middle moraines, displaying the flow direction of these glaciers. In locations where glaciers creep over steep terrain, cracks are visible. Similarly in terrestrial glaciers, cracks are formed when tensile stress within the ice increases due to greater slope and uneven terrain.

Further glacial features include elongated grooves, extending several kilometres, and elongated hills observed on the surface of mountain ridges some distance from potentially glaciated areas. These hills could be analogous to so-called 'drumlins', structures formed beneath ice by glacial flow resulting in compression and accumulation of abraded material. On Earth, drumlins appear in formerly glaciated regions such as Germany's Bavarian alpine uplands. These glacial structures are seen in a consistent spatial context, confirming the belief that scientists are really seeing former glaciers on Mars.

Of particular interest is the age of these glacially shaped surfaces, which seem to be fairly intact over a wide area of the formerly glaciated terrain. Typical evidence for a significant loss of ice volume, such as 'kettle holes' present in ice-free regions of Iceland, are almost entirely missing. The statistical analysis of the number of craters formed by meteorite impacts used for age determination also shows that part of the surface with its present-day glacial characteristics was formed only a few million years ago. In planetology, this age range is considered extremely young.

In these latitudes, ice on the surface of Mars is not stable over a long period of time due to the extremely thin atmosphere. In theory it is cold enough to allow for the existence of glaciers at the equator – summer day temperatures rise to a maximum of 20° C while night and winter time temperatures often drop below minus 50° C. But under the prevailing atmospheric pressure, ice would sublimate (transform directly from solid to gaseous state), and then escape from the atmosphere into outer space.

Therefore, glaciers must have formed until a few million years ago, in a time that was warmer and possibly also had a thicker atmosphere, and then became inactive or retreated due to the lack of continued supply of ice. Since then, they have been protected from sublimation by a thin dust layer. On Mars, dust is almost ubiquitous and would explain why 'fossil' ice present at depths of only a few metres could not be detected by other instruments such as spectrometers.

If these conclusions prove to be true, the results would indicate a climate change on Mars within the last million years. Such a dramatic climate change has been discussed for some years by Mars researchers. It could have been caused by a shift in the polar axis of the planet over millions of years – a phenomenon long known to scientists. Martian climate history is one of the main areas that ESA's Mars Express can help to decipher.

July 30, 2015  Some of the most breathtaking views in the Universe are created by nebulae -- hot, glowing clouds of gas. This new NASA/ESA Hubble Space Telescope image shows the center of ... read more

July 30, 2015  Comet Churyumov-Gerasimenko poses new riddles: Surface material measurements performed by the Philae landing module indicate that the near surface material might have changed ... read more

July 29, 2015  Physicists have revealed a new understanding of nucleosynthesis in stars, providing insight into the role massive stars play in the evolution of the Milky Way and the origins ... read more

July 28, 2015  A group of scientists have described developing and launching their imager, which centers on "Lobster-Eye optics," as well as its capabilities and future applications in space ... read more

Apr. 8, 2015  Mars has distinct polar ice caps, but Mars also has belts of glaciers at its central latitudes in both the southern and northern hemispheres. A thick layer of dust covers the glaciers, so they appear ... read more

Nov. 8, 2011  The latest image released from Mars Express reveals a large extinct volcano that has been battered and deformed over the eons. By Earthly standards, Tharsis Tholus is a giant, towering 8 kilometers ... read more

June 17, 2011  Earlier this month, ESA's Mars Express performed a special maneuver to observe an unusual alignment of Jupiter and the martian moon Phobos. The impressive images of this rare event are now ... read more